It would have been easy to find someone to take care of the kids for a weekend so that Brenda and Damon could go off and do their thing, but they apparently didn't see anything wrong with having a bunch of seedy people over at their house while their children were asleep. So little was the perceived threat that NOT ONCE did they check on their children the whole night. Maybe there really are "responsible swingers" in this world who are able to do their thing while adequately keeping their children out of danger. The VD's are anything but.
So I hope Mr and Mrs Van Dam pay the price for what they allowed to happen, while I still hold out hope that little Danielle will be found alive and placed with someone who actually cares about raising children.